The present invention pertains to improvements in folding tables, and more particularly in an improved lockable hinge for folding tables.
Folding tables are widely used in rooms that must be used for multiple purposes. The tables can be rapidly folded and put in storage, or set up in the room as may be required by circumstances. One popular type of prior art folding table comprises a pair of table surface members and means for hingeably interconnecting them along adjacent edges thereof. Leg assemblies are pivotally connected to the undersides of each of the table surface members, and cross connect links pivotally interconnect from the legs of one table surface member to the underside of the opposite table surface member. With this configuration, the table is foldable between a vertical storage position in which the table surface members and legs are generally vertically oriented for supporting the table in its folded position, and a horizontal usable position in which the table surface members are generally horizontally positioned and abutting along adjacent edges to define a table surface.
Locks have been provided for securing the table in its usable position so as to prevent inadvertent partial folding in case of excessive loads being applied to the outer edges of the table. One type of lock used on a table of this type in the prior art by the assignee of the present invention uses a pivoting locking bar positioned generally beneath the adjacent edges of the table and above and parallel to the hinge axis of the table. When unfolding the table, the bar falls by gravity action into notches provided in the hinge plates to lock the table in its down position. To fold the table, it is necessary to reach under the table to actuate a lever, rod or the like to release the latch.
It has recently been proposed to provide an additional locking function to stop folding tables just short of the horizontal usable position, when moving from the storage position. The purpose of such an intermediate locking function is to prevent the possibility of the operator accidentally getting his hand caught and pinched between adjacent edges of the table surface members as they come together towards abutment in the horizontal position. Often, depending upon the design of the table, the weight of the table tends to accelerate the unfolding operation as the table approaches the usable position, and an intermediate position lock will prevent the table from slamming abruptly to the open position.
It is not feasible to add an intermediate locking position to the prior art lockable hinge described in the second paragraph preceding by providing an additional set of notches for the locking bar, because of the position of the locking bar directly above the hinge axis between the adjacent edges of the table halves. Although this positioning of the locking bar works very well in the prior art locking hinge which has a lock only for the usable position of the table, it would be unacceptable in a device having an intermediate position lock because of the possibility that someone might try to place their hand between the adjacent edges of the table halves to release the locking bar.
One type of intermediate latch mechanism that has been proposed in the prior art involves the use of a separate spring operated latch and striker plate assembly near the center of the table. In this type of prior art device, the latch and striker plate operate completely independently of the hinges. A control rod runs from the latch to the side of the table to allow actuation thereof. The fact that the mechanism is independent of the hinges and is spring activated increases the number of parts and increases the cost of the table. In addition, the increased number of parts brings about an increased possibility that a part may be defective.
Another type of locking mechanism proposed in the prior art involves a rod which is mounted adjacent and parallel to the hinge axis between the adjacent edges of the table surface members. Ends or prongs of the rod pass through holes in hinge plates for one half of the table, to engage the edges of matting hinge plates for the other half of the table to form the intermediate lock, and to engage additional holes provided in the matting hinge plate to provide the lock for the usable position. The rod is held in the locked position by a spring, and is released by axially pulling the rod out of interference with the other hinge plate. Unfortunately this type of lock has the disadvantage of requiring a spring to engage the latch. Also, because of the necessary positioning of the rod between and beneath the adjacent edges, there is a chance that an operator might place a portion of his hand or thumb between the adjacent edges while releasing the latch to go from the intermediate to the full open positions of the table.